Thrust reversing apparatus

ABSTRACT

Apparatus includes housing to rear of jet nozzle to surround the gas stream. Housing has openings in wall to receive thrust reverser doors which close openings in stowed position and swing to deployed thrust reverse position with trailing edges together. Doors diverge forwardly and leading edges are adjacent housing wall. Doors are curved about longitudinal axis and have end plates at leading edges to divert gas stream forwardly. Each end plate is divided into segments along leading edge pivoted thereto for swinging from parallel to perpendicular position. Segments are overlapped to move as a unit while accommodating curvature of door. In one form, segments are forced to open position by gas flow and returned to stowed position by bumper when doors close. In an another form, yoke within door actuated by movement of doors acts through force linkage to positively swing segments in each direction.

United States Patent [72] Inventors Dale W. R. Lawson Bonita; FelixHorn, La Mesa; Richard U. Moeller, El Cajon, Calif. [21] Appl. No.862,725 [22 Filed Oct. 1,1969 [45] Patented Mar.l6,1971 [73] AssigneeRohr Corporation Chula Vista, Calif.

[54] THRUST REVERSING APPARATUS 15 Claims, 13 Drawing Figs.

[52] US. Cl ..239/265.29, 239/265 .31 [51] Int. Cl B64c 15/04 [50] Fieldof Search ..239/265.29, 265.27, 265.31; 60/229, 230

[ 5 6] References Cited UNITED STATES PATENTS 3,024,601 3/1962 Nash239/265.29X

3,280,561 10/1966 Kutney 3,483,702 12/1969 Ward Primary Examiner-M.Henson Wood, Jr. Assistant Examiner-John J. Love Attorney-George E.Pearson trailing edges together. Doors diverge forwardly and leadingedges are adjacent housing wall. Doors are curved about longitudinalaxis and have end plates at leading edges to divert gas streamforwardly. Each end plate is divided into segments along leading edgepivoted thereto for swinging from parallel to perpendicular position.Segments are overlapped to move as a unit while accommodating curvatureof door. In one form, segments are forced to open position by gas flowand returned to stowed position by bumper when doors close. In ananother form, yoke within door actuated by movement of doors actsthrough force linkage to positively swing segments in each direction.

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sum .5 or 5 INVENTOR- DALE W. R. LAWSON FELIX HOM RICHARD u. M ELLER BYEMA) ATTORNE THRUST REVERSING APPARATUS BACKGROUND OF THE INVENTION Thisinvention lies in the field of gas turbine engines, more commonly calledjet engines, which produce reaction thrust by ejecting a high-velocitystream of gas from the exhaust nozzle of the gas turbine. Airplanesdriven by jet engines fly and land at much higher speeds thanpropeller-driven aircraft. Their high landing speed puts a great burdenon the wheel brakes and of course they do not have propellers which arereadily reversible to produce reverse thrust. Therefore, it is necessaryto provide apparatus to reverse the gas stream to accomplish thisresult.

Various types of thrust reversers have been in use for many years. Allof them utilize a basic principle of blocking the rearward flow of theexhaust gas stream and diverting it laterally. If the stream has noforward component it will act in the manner of a speed brake byinterference with the free airstream, which is relatively ineffective.Normally, however, the stream is directed substantially forwardly toproduce an actual reverse thrust. A common type of thrust reverser haslateral openings in the wall of the nozzle or a housing in extension ofthe nozzle with deflector doors in the openings which close them instowed position. For reverse thrust the doors are swung inwardly andrearwardly with their trailing edges meeting at the center of thehousing to blockrearward flow, and the doors diverge forwardly to guidethe exhaust gases outwardly and forwardly.

A drawback of this general type of reverser is that, since the trailingedges must meet at the center, short doors must swing so far that theyhave very little forward component. If a substantial forward angle is tobe achieved with the leading edges as far outside the housing wall asdesired, the doors must be unreasonably long. One answer to this problemhas been the provision of deflector plates mounted on the inner wall ofeach reverser door pivoted to swing to deflecting position as the dooris deployed. The plates must be curved to lie flat on the inner faces ofthe doors in stowed position and their form makes them only partiallyeffective in active position. Moreover, they prevent smooth streamliningof the door inner wall for cruising flight where there is a requirementfor clearance and for ejector nozzle configurations.

Another answer is an end plate at the extreme leading edge of each doorsubstantially perpendicular to the door surface. It has been found thata fixed end plate standing only a few inches high at the leading edge isvery effective. It appears that the abrupt diversion of gas has theeffect of producing a virtual wall much higher than an aerodynamicallyshaped end plate of the same actual height. The difficulty with thisconstruction is that even these small end plates will project inwardduring normal cruising flight and, in many applications, will interferewith efficient operation.

SUMMARY OF THE INVENTION The present invention preserves the advantagesmentioned above while eliminating the problems which make the priordevices unsatisfactory. Generally stated, the apparatus includes ahousing which may be the nozzle or tailpipe or an additional housing incontinuation thereof, which receives and directs the exhaust gas stream.Openings in the wall of the housing are provided with doors which instowed position close the openings and in deployed position swing backand inward so that their trailing edges meet at the center of thehousing to block rearward flow of the gas stream and direct it laterallythrough the openings. End plates are provided at the leading edges ofthe doors.

In all forms of the invention each end plate is made up of a pluralityof segments which are individually pivotally mounted but which areoverlapped so that they move as a unit. In practically all cases thereverser doors are laterally curved about a longitudinal axis tocomplete the contour of a generally cylindrical housing. If a unitaryend plate is used, it must be curved to match the curvature of the doorwhen stowed. This makes it difficult to mount and in addition it is muchless effective in use. The segmental construction of the present endplates provides for a very satisfactory transition from a curved form instowed position to a planar form in deployed position.

In one form of the invention, a yoke is mounted between the spaced innerandouter walls of the door adjacent its leading edge, and is moved ashort distance fore and aft by actuating links connected to the housing.A plurality of force linkages connect the yoke to some of the. pivotedsegments so that movement of the yoke causes all of thesegments, becauseof the overlapping arrangement, to swing between stowed and deployedpositions. When stowed, the segments extend forward from the leadingedge of the door in streamline continuation to form a leading edge lipand complete the closure of the housing opening.

In a modified form, the pivoted segments extend rearwardly of theirpivotal mountings and lie on the inner wall of the door when they are instowed position. They are freely pivoted so that when the door opens;the gas stream passing forwardly swings the segments to theirperpendicular position where they are retained against further outwardmovement by suitable abutments. Bumper means are carried by the housingat the forward ends of the openings to intercept the segments shortlybefore the doors are completely closed. The relative movement of thedoors is such that the bumper means urge the segments rearward intotheir stowed positions.

While the invention is primarily intended for use in the constructiondescribed, it will be apparent that it can be applied equally well tothe external target-type reversers in which the doors swing to areversing position spaced behind the nozzle or other housing.

BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages and featuresof novelty will become apparent as the description proceeds inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a housing with the reverserdoors in stowed position;

FIG. 2 is a similar view showing the doors in deployed position;

FIG. 3 is a schematic side elevational view, partly in section, showinga first form of the invention;

FIGS. 4 and 5 are sectional views taken at different points on one of aplurality of vanes mounted on the doors, the vane being illustrated instowed position;

FIG. 6 is a view taken on line 6-6 of FIG. 3;

FIG. 7 is a schematic side elevational view, partly in section, showingthe door and end plate segments of FIG. 3 in deployed position;

FIG. 8 is a schematic side elevational view of a second form of theinvention, with the door in stowed position;

FIG. 9 is a view similar to FIG. 8, with the door in deployed position;

FIG. 10 is a schematic side elevational view, partly in section, showinga third form of the invention, with the door approaching stowedposition;

FIG. 11 is a view similar to FIG. 10, with an end plate segmentcontacting the bumper means;

FIG. 12 is a view similar to FIG. 10, showing the segments partiallyfolded; and

FIG. 13 is a view similar to FIG. 10, showing the segments fully stowed.

DESCRIPTION OF PREFERRED EMBODIMENTS The apparatus of this invention maybe used with any general type of engine installation, such as pod, wing,or fuselage mounting. For convenience of illustration it is shownschematically in FIGS. 1 and 2 as including a housing 10 provided withreverser doors 12, the housing being mounted as a continuation of thetail pipe or nozzle 14 of an engine not shown.

In FIG. I, the doors are shown in closed or stowed position with the endplates 16 parallel to the doors and extending forward to complete theclosure of openings 18 in the housing. In FIG. 2 the doors are shown inopen or deployed position with the end plates 16 extending inward andforward generally perpendicular to the inner walls of the doors. Thetrailing edges 20 of the doors meet substantially at the center of thehousing to block the rearward flow of the exhaust stream and direct itlaterally and forwardly through the openings 18 to produce reversethrust.

As can be seen in FIG. 2, the doors themselves may have little or noforward component, extending at an angle of about 75 to 100 to thehousing axis. The major part or all of the thrust reversal isaccomplished by the provision of the end plates 16. The abrupt abutmentpresented by the provision of the end plates 16. The abrupt abutmentpresented by each end plate very forcefully diverts the gas streamforwardly to produce a very high reverse thrust component. With a plateheight of to percent of a nozzle diameter, reverse thrust has beendeveloped amounting to as much as 60 percent of the full forward thrustof the engine.

One detailed form of the invention is shown in FIGS. 3 to 7, which alsoshow in broken lines a suitable mechanism, not a part of the presentinvention, for moving the doors of any of the forms between stowed anddeployed positions. Briefly, each door 12 is provided at each of itslongitudinally extending lateral margins 22 with a pivotal connection 24to the wall of the housing for swinging about a lateral axisperpendicular to the axis of the housing. When the door is deployed asseen in FIG. 7, its leading edge 26 is adjacent the wall of the housingand its trailing edge is generally at the center of the housing,cooperating with the other door or doors to block rearward flow of thegas stream and direct it laterally. End plates 16 then redirect thestream forwardly almost parallel to the axis of the housing.

A crank arm 28 is fixedly connected to the door at pivotal mounting 24and in the stowed position of said door extends rearwardly as seen inFIG. 3. Its free end is pivotally connected at 30 to a link 32 which inturn is pivotally connected to bogie 34 slidably mounted on tracks 36.The bogie is actuated by a servomotor, not shown, and moves forward toswing the door to deployed position and moves rearward to swing the doorto stowed position. i

It will be noted that each door 12 is laterally curved about alongitudinal axis such as the axis of the housing. If a unitary endplate were used, it would necessarily have the curvature of the door andit would be difficult if not impossible to shape it and mount it so thatit would provide a uniform abutment in action and be rigidly heldagainst the high gas stream forces. The present construction overcomesthis difficulty by the use of a plurality of end plate segmentsindividually pivotally mounted to the leading edge of the door and ofsubstantially the same dimensions. Although each segment is almost flat,the total assembly closely follows the door contour.

All of the segments are hollow and have triangular cross sections. Thesegments 38 are larger than the segments 40 and the latter fit slidablyin the former to produce an overlapping assembly which moves as a unit.Each segment has at least one and preferably two pivotal mountings atthe leading edge of the door adjacent its inner wall 42. A typicalmounting is bracket 44, FIG. 5, having a pivot pin 46 on which segment38 swings. In most cases, each segment is carried by two of thesebrackets. In FIG. 4, the support is in the form of a rail or guide track48 which serves another purpose to be described later. Track 48 isrigidly mounted in the door and at its forward end is provided with apivot pin 50 on which segment 38 swings.

Force applying means to case segment 38 to swing between stowed anddeployed positions is seen in FIG. 4 as a force link 52 which is axiallyslidable and is provided at its forward end with a pivot pin 54 forconnection to the outer rear edge of segment 38 close to the outer wall56 of the door. Forward movement of force link 52, to the left as seenin FIG. 4, forces segment 38 to swing clockwise to a deployed positiongenerally perpendicular to inner wall 42 of the door, and rearwardmovement of the force link causes the segment to return to stowedposition extending forwardly of its pivotal mounting in generalstreamline continuation of the door. A force link may be applied to allor only some of the segments 38. In any event, enough links are used toensure uniform operation. Since all of segments 38 and 40 are overlappedas described, the free swing segments will necessarily move with thedriven segments, and the entire end plate assembly will gradually changefrom arcuate to planar form as it deploys.

As will be seen in FIGS. 3, 6, and 7, a plurality of guide tracks 48 arespaced evenly across the lateral extent of the door and serve to supportthe force transmitting means which moves the force links 52. The forcetransmitting means comprises a rigid elongate bar 58 extending laterallybetween the inner and outer walls of the door from margin to margin andcurved to conform to the curvature of the door and form a yoke. The yokeis provided with a bearing 60 for slidable mounting on each guide track48 as best seen in FIG. 6. Each bearing includes a bracket 62 having apivot pin 64 to which is connected the aft end of one of the force links52. Thus, the fore and aft sliding movement of the yoke causes acorresponding fore and aft movement of all of the force links and theswinging of all of the segments.

Force initiating means are provided to produce the necessary fore andaft sliding movement of the yoke. One such mechanism is located at eachlateral margin of the door. Since they are alike in form and action,only one will be described. Referring to FIGS. 3 and 6, an actuatinglink 66 is connected at its forward end within the door to an end ofyoke 58 and is also slidably mounted in the door by means of a pin 68which rides in a slot 70 (FIG. 7) in support guide 72 which is fixedlymounted in the door. The aft end of link 66 is pivotally connected toanchor pin 74 which is fixedly mounted in the housing adjacent the doormargin and is offset downwardly, as seen in FIG. 3, from the pivotalmounting 24 of the door. As the door swings from the FIG. 3 position tothe FIG. 7 position, the forward end of link 66 moves forward withrespect to the door and moves yoke 58 forward to the same extent. Theforward movement of the yoke causes deployment of the segments aspreviously described in their FIG. 7 positions.

A modified force linkage is illustrated in FIGS. 8 and 9 for use incases where the gas stream force on the end plates is very high. In thisform the force initiating means and force transmitting means are thesame as in the first form, and the end plate segments are formed,arranged, and pivotally mounted in the same way. Force links 52 arereplaced by elongate cam members 76, each of which is fixedly connectedat its aft end to a bracket 62 on the yoke. The forward end is providedwith a cam face 78 angling inwardly and rearwardly. In the stowedposition the cam face is in contact with the outer rear comer 80 of theend plate segment, as seen in FIG. 8.

When the yoke moves the cam member forwardly, cam face 78 forces corner80 forward and inward to the FIG. 9 position, and the body of the cammember underlies the segment and positively prevents its return to theFIG. 8 position. Rearward movement of the cam member allows the segmentto swing to stowed position. However, it cannot positively pull thesegment back and hold it. For this purpose, tie link 82 is provided andis pivotally connected at its aft end to cam member 76 by pin 84. Thetie link is provided with an elongate slot 86 which has a lost-motionconnection with pin 88 on the segment. Thus the tie link does notinterfere with the deploying movement. However, as the cam memberreturns to stowed position, pin 88 reaches the end of slot 86 and thetie link positively pulls the segment to stowed position and holds itagainst movement.

A further modified form of the invention is shown in FIGS. 10 to 13 inwhich the end plate segments in stowed position extend rearwardly fromtheir pivotal mountings to lie along the inner wall 42 of the door 12and substantially parallel thereto. In this case the segments may be inthe form of single thickness plates 90 and 92 which may be arranged inalternately overlapping relation. Each segment is pivotally mounted bypin 94 to a bracket 96 secured to the leading edge of the door and isfree swinging. FIG. illustrates a door in the deployed position, atwhich time the end plate segments are substantially perpendicular toinner wall 42 of the door. A corner or abutment 98 at the pivot edge ofeach segment engages the associated bracket 96 to prevent furtherforward movement of the segment relative to the door.

Bumper means are provided in the form of an inwardly angled strip 100which is secured to the inner wall of housing 10 and extends laterallyfor the full width of opening 18 in the housing and also extends a shortdistance rearwardly of the forward edge 102 of the opening l8. As thedoor is being deployed and reaches the position illustrated in FIG. 11,the segments 90 and 92 disengage from strip 100 and then the pressure ofthe exhaust stream impinging upon the aft sides of said segments swingsthe latter to the position illustrated in FIG. W. The strip 100 is sodimensioned and positioned that, as the leading edge of the door movestoward stowed position along path 104, the free edges 106 of. thesegments 90 will contact the free edge 108 of the strip 100 as seen inFIG. 11. As closing is completed through FIGS. 12 and 13, the bumperstrip gradually causes the segments to fold down into stowed positionsubstantially parallel with the inner wall 42 of the door R2. The gapbetween the housing wall and the bumper strip receives the leading edgeof the door so that a smooth streamlined contour is achieved for normalcruising flight.

We claim:

1. Thrust reversing apparatus for use in combination with a jet engineand adapted to be mounted aft of the exhaust outlet for controlling theflow of exhaust gas therefrom, comprising: an open-ended housing toreceive and direct the exhaust gas flow; openings in the sidewall of thehousing; a thrust reverser door mounted in each opening and swingablebetween a stowed position closing said opening and a deployed positionin which the trailing edges cooperate to block rearward axial flowthrough the housing and each door extends outwardly and forwardly fromthe center of the housing with its leading edge adjacent to the housingwall; the leading edge of each door comprising a plurality of end platesegments arranged laterally adjacent to each other in overlappingrelation to form a substantially continuous leading edge lip; saidsegments being pivotally mounted at said leading edge and swingablebetween stowed positions lying generally parallel to the door anddeployed positions extending inward of the door and generallyperpendicular thereto; and means acting in response to movement of thedoor to stowed position to cause said segments to move to their stowedpositions.

2. apparatus as claimed in claim 1, said segments in their stowedpositions extending rearwardly of their pivotal mountings along theinner wall of the door and being freely mounted to be swung to theirdeployed positions by the force of the exhaust gas flow against them.

3. Apparatus as claimed in claim 2; said means comprising bumper meansfixedly mounted at the leading edge of the opening in the housing andposition to contact the free edges of of at least some of the segmentsand cause the segments to swing rearwardly to a position of substantialparallelism with the inner wall of the door.

4. Apparatus as claimed in claim 3; said bumper means comprisingagenerally continuous strip fixedly secured to the inner wall of thehousing and extending rearwardly of the leading edge of the opening tointercept the free edges of the segments as the door approaches fullystowed position.

5. Apparatus as claimed in claim 1; said segments in their stowedpositions extending forwardly of their pivotal mountings andconstituting a forward streamlined continuation of the door to form acomplete closure for the housing opening.

6. Apparatus as claimed in claim 5; said door having inner and outerspaced walls; and said means to cause said segments to move to stowedposition being constructed to also cause said segments to move todeployed position; said segment moving means being mounted within saiddoor between its inner a outer walls.

7. Apparatus as claim 6; said segment moving means including forceinitiating means movable in response to swinging movement of said door,force transmitting means connected to said force initiating means andmovable thereby, and force applying means connected between said forcetransmitting means and at least some of said segments and movable toswing aid segments between stowed and deployed positions.

8. Apparatus as claimed in claim 7; said door having lateral marginsextending in a fore and aft direction; an anchor pivot mounted in thehousing adjacent to each of said margins and offset from the effectiveaxis of rotation of the door; a support guide mounted at each margin ofthe door adjacent to its leading edge; and said force initiating meanscomprising an actuating link extending in a fore and aft direction ateach margin of the door and having a first end pivotally connected tosaid anchor pivot and a second end movably connected to said supportguide.

9. Apparatus as claimed in claim 7; said door having lateral marginsextending in a fore and aft direction; a plurality of guide trackswithin the door adjacent to its leading edge and laterally spacedbetween the margins and extending parallel to each other in a fore andaft direction; and said force transmitting means comprising a rigidelongate bar extending laterally substantially from margin to marginadjacent to the leading edge; said bar having bearing members slidablymounted on said guide tracks to provide fore and aft movement of saidbar.

10. Apparatus as claimed in claim 9; said door being laterally curvedabout a longitudinal axis and said bar being correspondingly curved toform a yoke.

11. 1. Apparatus as claimed in claim 7; said door having lateral marginsextending in a fore and aft direction; segment support pivots secured tothe leading edge of the door adjacent to the inner wall thereof andarranged in spaced relation from margin to margin, with at least onepivot for each segment; said segments being mounted on said pivots 'forswinging inwardly from stowed streamlined position to deployed positiongenerally perpendicular to the inner wall of the door; and said forceapplying means comprising a plurality of force linkages arranged inspaced relation along the leading edge of the door from margin tomargin, connected at their aft ends to said force transmitting means andat their forward ends to outer portions of adjacent segments; saidlinkages being movable forwardly to deploysaid segments and rearwardlyto stow said segments.

12. Apparatus as claimed in claim 11; the linkage-driven segments actingthrough their overlapping relation to swing those segments which are notconnected to the linkages.

l3. apparatus as claimed in claim 11; each of said force linkagescomprising an elongate link pivotally connected at its aft end to theforce transmitting means and pivotally connected at its forward end toone of said segments. v

14. Apparatus as claimed in claim 11; each of said force linkagescomprising an elongate cam member connected at its aft end to the forcetransmitting means and having a cam face at its forward end to engagethe outer rear edge of the adjacent segment and movable forwardly toforce the segment to rotate inward to deployed position and underlie thesegment to prevent its return to stowed position; and a tie linkpivotally connected to said segment and said cam member andincorporating lost motion; rearward movement of said cam member removingthe cam face from blocking position and drawing the tie link rearwardlyto positively return the segment to fully stowed position.

15. Apparatus as claimed in claim 6; said door being laterally curvedabout a longitudinal axis and having lateral margins extending in a foreand aft direction; said segment moving means comprising an actuatinglink pivotally connected at a first end to the housing at a point offsetfrom the effective axis of rotation of the door and slidably connectedat its second end to the door; a curved yoke within the door adjacent tothe leading edge thereof and slidably mounted therein for fore and aftmovement; said yoke extending substantially from margin to margin of thedoor and having one aft movement; and force linkages connected betweensaid yoke and a plurality of said segments to swing them between stowedand deployed positions in response to the fore and aft movement oftheyoke.

1. Thrust reversing apparatus for use in combination with a jet engineand adapted to be mounted aft of the exhaust outlet for controlling theflow of exhaust gas therefrom, comprising: an open-ended housing toreceive and direct the exhaust gas flow; openings in the sidewall of thehousing; a thrust reverser door mounted in each opening and swingablebetween a Stowed position closing said opening and a deployed positionin which the trailing edges cooperate to block rearward axial flowthrough the housing and each door extends outwardly and forwardly fromthe center of the housing with its leading edge adjacent to the housingwall; the leading edge of each door comprising a plurality of end platesegments arranged laterally adjacent to each other in overlappingrelation to form a substantially continuous leading edge lip; saidsegments being pivotally mounted at said leading edge and swingablebetween stowed positions lying generally parallel to the door anddeployed positions extending inward of the door and generallyperpendicular thereto; and means acting in response to movement of thedoor to stowed position to cause said segments to move to their stowedpositions.
 2. apparatus as claimed in claim 1, said segments in theirstowed positions extending rearwardly of their pivotal mountings alongthe inner wall of the door and being freely mounted to be swung to theirdeployed positions by the force of the exhaust gas flow against them. 3.Apparatus as claimed in claim 2; said means comprising bumper meansfixedly mounted at the leading edge of the opening in the housing andposition to contact the free edges of of at least some of the segmentsand cause the segments to swing rearwardly to a position of substantialparallelism with the inner wall of the door.
 4. Apparatus as claimed inclaim 3; said bumper means comprising a generally continuous stripfixedly secured to the inner wall of the housing and extendingrearwardly of the leading edge of the opening to intercept the freeedges of the segments as the door approaches fully stowed position. 5.Apparatus as claimed in claim 1; said segments in their stowed positionsextending forwardly of their pivotal mountings and constituting aforward streamlined continuation of the door to form a complete closurefor the housing opening.
 6. Apparatus as claimed in claim 5; said doorhaving inner and outer spaced walls; and said means to cause saidsegments to move to stowed position being constructed to also cause saidsegments to move to deployed position; said segment moving means beingmounted within said door between its inner a outer walls.
 7. Apparatusas claim 6; said segment moving means including force initiating meansmovable in response to swinging movement of said door, forcetransmitting means connected to said force initiating means and movablethereby, and force applying means connected between said forcetransmitting means and at least some of said segments and movable toswing aid segments between stowed and deployed positions.
 8. Apparatusas claimed in claim 7; said door having lateral margins extending in afore and aft direction; an anchor pivot mounted in the housing adjacentto each of said margins and offset from the effective axis of rotationof the door; a support guide mounted at each margin of the door adjacentto its leading edge; and said force initiating means comprising anactuating link extending in a fore and aft direction at each margin ofthe door and having a first end pivotally connected to said anchor pivotand a second end movably connected to said support guide.
 9. Apparatusas claimed in claim 7; said door having lateral margins extending in afore and aft direction; a plurality of guide tracks within the dooradjacent to its leading edge and laterally spaced between the marginsand extending parallel to each other in a fore and aft direction; andsaid force transmitting means comprising a rigid elongate bar extendinglaterally substantially from margin to margin adjacent to the leadingedge; said bar having bearing members slidably mounted on said guidetracks to provide fore and aft movement of said bar.
 10. Apparatus asclaimed in claim 9; said door being laterally curved about alongitudinal axis and said bar being correspondingly curved to form ayoke.
 11. 1. Apparatus as claimed in claim 7; said door having lateralmargIns extending in a fore and aft direction; segment support pivotssecured to the leading edge of the door adjacent to the inner wallthereof and arranged in spaced relation from margin to margin, with atleast one pivot for each segment; said segments being mounted on saidpivots for swinging inwardly from stowed streamlined position todeployed position generally perpendicular to the inner wall of the door;and said force applying means comprising a plurality of force linkagesarranged in spaced relation along the leading edge of the door frommargin to margin, connected at their aft ends to said force transmittingmeans and at their forward ends to outer portions of adjacent segments;said linkages being movable forwardly to deploy said segments andrearwardly to stow said segments.
 12. Apparatus as claimed in claim 11;the linkage-driven segments acting through their overlapping relation toswing those segments which are not connected to the linkages. 13.apparatus as claimed in claim 11; each of said force linkages comprisingan elongate link pivotally connected at its aft end to the forcetransmitting means and pivotally connected at its forward end to one ofsaid segments.
 14. Apparatus as claimed in claim 11; each of said forcelinkages comprising an elongate cam member connected at its aft end tothe force transmitting means and having a cam face at its forward end toengage the outer rear edge of the adjacent segment and movable forwardlyto force the segment to rotate inward to deployed position and underliethe segment to prevent its return to stowed position; and a tie linkpivotally connected to said segment and said cam member andincorporating lost motion; rearward movement of said cam member removingthe cam face from blocking position and drawing the tie link rearwardlyto positively return the segment to fully stowed position.
 15. Apparatusas claimed in claim 6; said door being laterally curved about alongitudinal axis and having lateral margins extending in a fore and aftdirection; said segment moving means comprising an actuating linkpivotally connected at a first end to the housing at a point offset fromthe effective axis of rotation of the door and slidably connected at itssecond end to the door; a curved yoke within the door adjacent to theleading edge thereof and slidably mounted therein for fore and aftmovement; said yoke extending substantially from margin to margin of thedoor and having one end connected to said actuating link to produce saidfore and aft movement; and force linkages connected between said yokeand a plurality of said segments to swing them between stowed anddeployed positions in response to the fore and aft movement of the yoke.